PERSPECTIVES
COMPUTER SCIENCE
How online personas are designed may
increase the impression of trustworthiness, but
that does not make the information conveyed
more reliable.
Virtually Trustworthy
Judith Donath
CREDIT: DIETMAR OFFENHUBER
O
stand next to each other to talk, but stare blankly
into space, inert and unengaged.
Just giving the user finer control over the
avatar is not a satisfactory option, however, for
if users must specify their avatar’s every eye
movement and gesture, they would be too distracted to engage in the conversation itself.
Cassell and Vilhjálmsson’s solution was to
program such behaviors into the avatars, to be
set off when the user indicated some desired
action. For instance, if the user indicated (with
a simple typed command) that she wanted to
end a conversation, the avatar would break
away by averting its gaze, and upon leaving
would look at its recent partner, nod its head,
and wave. Users of this system found it more
natural and engaging than one with static
avatars and felt that their conversational partners were more expressive.
Researchers have found that users infer a
number of character traits from avatar behavior
and appearance. They judge avatars that are
humanlike and clearly gendered (as opposed to
androgynous) to be the most attractive and the
most credible (2). In an audio-only conversation, simply adding an avatar whose head and
eye movements match the conversation flow
increases users’ perception of their partners’
trustworthiness and friendliness.
Today’s online graphical interactions are
still rather awkward. Behavioral sophistica-
Held in trust.
Self presentation
in real and
virtual life.
The author is at the Massachusetts Institute of Technology
Media Lab, Cambridge, MA 02139, USA. E-mail: judith@
media.mit.edu
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VOL 317
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tion lags behind rendering skill, so we have
avatars whose appearance raises high expectations of humanlike behaviors but whose gaze
and gestures are relatively primitive. However,
it is quite conceivable that in a few years
avatars whose behavior is nearly imperceptible from humans’ will be available.
Yet this raises important questions about
the reliability of the impressions we form in
avatar-mediated interactions. In our face-toface interactions, many of the cues we read to
assess traits such as trustworthiness have real
links to the trait. Gaze direction, for example,
links directly to what one is seeing. When long
averted, it is thus a sign of inattention. During
times of high cognitive load, such as when
inventing a story, people may make less eye
contact, possibly because gazing at another
face is itself a cognitively intensive process.
Perhaps because of this, we have the popular
(though unsubstantiated) belief that someone
who makes steady and direct eye contact is
being honest (3).
Online, however, behaviors generated by a
software program can create the same impression of trustworthiness or friendliness, but
without a grounding connection to an underlying cognitive process or other causative element. As behavioral software becomes more
sophisticated, are we creating avatars that will
be increasingly attractive and seemingly
friendly but are in fact the ideal mask behind
which a dishonest or manipulative person can
operate? Once an interface includes humanlike avatars, the issue of user interpretation of
character traits from ungrounded avatar
behaviors is inevitable, for even nonaction is
an interpretable behavior; it conveys an
impression of social ineptness and distance.
How we assess these issues depends on the
context in which they are used and how we
view them in relation to real-world practice. In
the real world, we use many strategies to
enhance the impression we make on others.
We employ resume consultants and speech
coaches, wear makeup, and undergo plastic
surgery. In the virtual realm, idealized bodies
and perfect skin are the norm (2), but there are
also a whole new range of possible enhancements. Bailenson and colleagues have conducted several experiments on digital mimicry, such as morphing a person’s own face
into the avatar of their conversational partner
or having that avatar closely mimic their ges-
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ur impression of others in face-toface interactions derives from multimodal observations: We hear voices,
see faces and gestures, and listen to each
other’s words. Our online interactions are less
sensory, dominated instead by text: We send email, read discussion boards, and participate
in text chats. Yet that may be changing. Online
3D spaces such as There and Second Life feature detailed virtual environments in which
users represent themselves with graphical
avatars, often highly customizable.
Avatars may closely resemble a person, or
they may be fantastical creations such as
aliens or talking lizards. Their online use dates
back to the mid-1980s, when they were used
in games such as Ultima and in the online
social space Habitat. As technology has
advanced, they have gone from being static
2D images to complex 3D animations, complete with realistic gait, fashionable clothing,
and dynamic facial expressions.
The challenge in creating more sophisticated avatars lies partly in the domain of computer graphics, such as better rendering of hair
and fabric or more lifelike gait kinematics. Yet
there is also a substantial social element: getting the avatar to interact with others gracefully and realistically. For example, if an
avatar is rendered with detailed eyes, then
appropriate gaze direction is essential. All
such behaviors, which are taken for granted in
face-to-face interaction, must be explicitly
coded into the avatar.
We carry out social interactions with a large
number of communicative behaviors that indicate our intention, state of mind, communicative competency, and so on. For instance, you
may see an acquaintance across the room at a
cocktail party and decide to go speak to him.
You carry out this goal not only by walking
across the room but also by making eye contact,
smiling, raising your brows, adjusting your
clothes—a complex set of communicative
behaviors that indicate your intention to start a
conversation, allow you to gauge his willingness to do so, and show your level of determination. Cassell and Vilhjálmsson (1) argued that
avatars without these social behaviors seem
stilted and awkward. They can be moved to
53
PERSPECTIVES
tures (4). They found that people in a group
paid closer attention to messages delivered by
a “team face” avatar, made by combining the
features of the people in the group. This could
be a useful technique for enhancing the cohesiveness of geographically dispersed groups.
Yet they also found that politicians’arguments
were more persuasive when their faces were
made to subtly resemble the listener’s, raising
the specter of a world in which you are bombarded with oddly compelling ad campaigns
presented by people just like you.
Reliability involves tradeoffs. Less reliable
communication is often cheaper or easier;
when deception becomes too prevalent, more
costly signals or social sanctions may be
needed (5). Suspicious citizens of the future
may demand to interact with candidates only
through trusted “manipulation-free” sites.
Today, most 3D graphical sites are fantasy
games, where role-playing and artifice are not
only accepted but also required. As social sites
such as Second Life gain popularity, other uses
are emerging, including academic lectures,
retail stores, and business meetings. These
will require a range of avatar designs, not only
in terms of technical sophistication but also
across a continuum from the most attractive
and impressively persuasive to the most rigorously and reliably grounded.
References
1. J. Cassell, H. Vilhjálmsson, Autonomous Agents and
Multi-Agent Systems 2, 45 (1999).
2. K. L. Nowak, C. Rauh, J. Computer-Mediated Comm. 11,
153 (2005).
3. B. M. DePaulo et al., Psychol. Bull. 129, 74 (2003).
4. J. N. Bailenson, A. C. Beall, in Avatars at Work and Play:
Collaboration and Interaction in Shared Virtual
Environments, R. Schroeder, A. Axelsson, Eds. (SpringerVerlag, London, 2006), pp. 1–16.
5. J. Donath, Signals, Truth, and Design (MIT Press,
Cambridge, MA, in press).
10.1126/science.1142770
Shining Light on the Rapidly
Evolving Structure of Water
Time-resolved infrared spectroscopy is
shedding light on the dynamics of hydrogen
bonding in liquid water.
Andrei Tokmakoff
he molecular origins of the physical
properties of water continue to puzzle
scientists. Each tool provides only a
limited perspective, revealing certain aspects
of the hydrogen-bonding structure or of the
ultrafast time scales over which the structure
changes. Now, a new generation of timeresolved vibrational spectroscopies is providing detailed insights into how the structure of
water evolves. The results raise questions
about the nature of hydrogen bonding.
The structure of liquid water is generally
conceived as a disordered network of molecules connected by hydrogen bonds (1). This
structure fluctuates and reorganizes on time
scales between 10 fs (10–14 s) and 10 ps (10−11 s).
This hydrogen-bond dynamics is at the heart
of the unique physical, chemical, and biological properties of water. Insights into its structural properties have come from x-ray and
neutron-scattering experiments, which lack
dynamical information; insights into its
dynamics have been gained from ultrafast
time-resolved experiments, which have
lacked structural detail. The most detailed
understanding of liquid water derives from
molecular dynamics simulations, which commonly treat the liquid as rigid molecules with
charges. Such simulations provide an atomby-atom perspective on how hydrogen bonding changes with time, but their dynamics have
never been properly tested against experiment.
T
The author is in the Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139,
USA. E-mail: tokmakof@mit.edu
54
Femtosecond infrared spectroscopy bridges scales of 48 fs, 400 fs, and 1.4 ps, and attribthe gap between these methods by providing a uted the short times to fluctuations in the
structure-sensitive probe of how the hydrogen- hydrogen bonds and the long times to hydrobond network in liquid water evolves. In these gen-bond breaking and forming. These results
studies, hydrogen bonding is probed by moni- were qualitatively similar to simulations, but
toring the frequency of the O-H bond–stretch- the time scale for hydrogen-bond breaking was
ing vibration, which decreases with increased nearly two times slower than for the widely
strength of the hydrogen bond in which it used SPC/E and TIP4P water models. Fecko et
participates. The newest method of two-dimen- al. made similar observations for HDO in D2O
sional infrared spectroscopy (2D IR) uses using the related technique of echo peak shift
ultrafast infrared light pulses to track how spectroscopy. In addition to 50-fs fluctuations,
the frequencies of different O-H
bonds evolve with time.
However, spectroscopy cannot
tell you everything. Simulations
are important for providing the
structural interpretation of the
experiments, drawing on a theoretical description of how the O-H
frequency is determined by hydrogen-bonding structure (2–4). This
interpretation tool has initiated a
feedback process in which the simulation describes how structural
changes appear in the experiment,
and the experiment provides the
benchmark for the computer model.
Asbury et al. were the first to
perform 2D IR experiments on
water (5). By studying the isolated
Switching a hydrogen bond. In this 288-fs sequence taken from
O-D vibration of dilute HDO in
a classical simulation, structural fluctuations induce the switching
2
H2O (D is the H isotope), they of a hydrogen bond between the donor molecule (bottom) and an
mapped the time scales over which acceptor molecule (upper left) to a new acceptor (upper right). The
a water molecule samples different hydrogen-bond connectivity is color coded, showing the rotation
hydrogen-bonding configurations. from the initial acceptor (blue) through the bifurcated state (green)
They observed dynamics on time to the approaching new acceptor (orange).
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CHEMISTRY